Subspace of Either-Or Space less Zero is not Lindelöf

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Let $T = \struct {S, \tau}$ be the either-or space.

Let $H = S \setminus \set 0$ be the set $S$ without zero.

Then the topological subspace $T_H = \struct {H, \tau_H}$ is not a Lindelöf space.


By definition of topological subspace, $U \subseteq H$ is open in $T_H$ if and only if:

$(1): \quad \set 0 \nsubseteq U$


$(2): \quad \openint {-1} 1 \subseteq U$

But for all $U \subseteq H$, condition $(1)$ holds as $0 \notin H$.

So $T_H$ is by definition a discrete space.

As $T_H$ is uncountable, we have that Uncountable Discrete Space is not Lindelöf holds.

Hence the result.